This project examines the mechanisms by which gonadotropin releasing hormone (GnRH) controls the secretion of LH and FSH by anterior pituitary cells. This includes characterization and analysis of the GnRH receptors in anterior pituitary cells and membranes, and the roles of calcium, cyclic nucleotides and other intracellular regulators in the mechanism of action of GnRH. Receptors for GnRH have been shown to be regulated by the releasing hormone, which causes an increase in its pituitary binding sites, and by gonadal steroid hormones. The mechanism by which GnRH stimulates gonadotropin release has been shown to be unrelated to cyclic nucleotides, but is highly dependent on calcium, and current studies suggest that phospholipid metabolites, especially arachidonic acid and its derivatives, may have an important function as mediators of GnRH action.